Silicon-containing photoresist for lithography

ABSTRACT

A photoresist composition and methods of using the same are disclosed. The photoresist includes a polymer backbone, an acid labile group (ALG) chemically bonded to the polymer backbone, a photo-acid generator (PAG), a solvent, and a silicon-containing unit that is chemically bonded to one of: the ALG and a crosslinker. A method of using the photoresist composition includes forming a layer of the photoresist over a substrate, performing an exposing process to the photoresist layer; and developing the photoresist layer, thereby forming a patterned photoresist layer. The patterned photoresist layer includes the silicon-containing unit.

BACKGROUND

The semiconductor integrated circuit (IC) industry has experiencedexponential growth. Technological advances in IC materials and designhave produced generations of ICs where each generation has smaller andmore complex circuits than the previous generation. In the course of ICevolution, functional density (i.e., the number of interconnecteddevices per chip area) has generally increased while geometry size(i.e., the smallest component (or line) that can be created using afabrication process) has decreased. This scaling down process generallyprovides benefits by increasing production efficiency and loweringassociated costs. Such scaling down has also increased the complexity ofprocessing and manufacturing ICs.

Photolithography has been used for patterning a substrate (e.g., awafer) in order to form various features of an IC. In a typicalphotolithography process, a resist layer is formed over a substrate andis exposed to a radiation to form latent images of an IC. Subsequently,it is developed in a developer (a chemical solution) to remove portionsof the resist layer, thereby forming a resist pattern. The resistpattern is then used as an etch mask in subsequent etching processes,transferring the pattern to an underlying material layer. To be used asan etch mask, the resist pattern must exhibit certain etching resistancein the subsequent etching processes. Presently, there is a need for newand improved resist materials that provide increased etching resistanceover existing resist materials.

BRIEF DESCRIPTION OF THE DRAWINGS

The present disclosure is best understood from the following detaileddescription when read with the accompanying figures. It is emphasizedthat, in accordance with the standard practice in the industry, variousfeatures are not drawn to scale and are used for illustration purposesonly. In fact, the dimensions of the various features may be arbitrarilyincreased or reduced for clarity of discussion.

FIG. 1 illustrates a flow chart of a lithography patterning methodaccording to various aspects of the present disclosure.

FIGS. 2A, 2B, 2C, 2D, 2E, and 2F illustrate cross-sectional views offorming a target pattern according to the method of FIG. 1, inaccordance with an embodiment.

FIGS. 3A and 4A illustrate exemplary structures of a photoresistconstructed according to aspects of the present disclosure.

FIGS. 3B and 4B illustrate structures of the photoresist of FIGS. 3A and4A, respectively, during a step performed in the method of FIG. 1, inaccordance with an embodiment.

FIG. 5 illustrates exemplary structures of a crosslinker component in aphotoresist constructed according to aspects of the present disclosure.

FIGS. 6A, 6B, 6C, 6D, 6E, 6F, and 6G illustrate exemplary structures ofa silicon-containing component in a photoresist constructed according toaspects of the present disclosure.

FIGS. 7A, 7B, 7C, 7D, 7E, and 7F illustrate cross-sectional views offorming a target pattern according to the method of FIG. 1, inaccordance with another embodiment.

FIG. 8A illustrates an exemplary structure of a photoresist constructedaccording to aspects of the present disclosure.

FIG. 8B illustrates a structure of the photoresist of FIG. 8A during astep performed in the method of FIG. 1, in accordance with anembodiment.

DETAILED DESCRIPTION

The following disclosure provides many different embodiments, orexamples, for implementing different features of the provided subjectmatter. Specific examples of components and arrangements are describedbelow to simplify the present disclosure. These are, of course, merelyexamples and are not intended to be limiting. For example, the formationof a first feature over or on a second feature in the description thatfollows may include embodiments in which the first and second featuresare formed in direct contact, and may also include embodiments in whichadditional features may be formed between the first and second features,such that the first and second features may not be in direct contact. Inaddition, the present disclosure may repeat reference numerals and/orletters in the various examples. This repetition is for the purpose ofsimplicity and clarity and does not in itself dictate a relationshipbetween the various embodiments and/or configurations discussed.

Further, spatially relative terms, such as “beneath,” “below,” “lower,”“above,” “upper” and the like, may be used herein for ease ofdescription to describe one element or feature's relationship to anotherelement(s) or feature(s) as illustrated in the figures. The spatiallyrelative terms are intended to encompass different orientations of thedevice in use or operation in addition to the orientation depicted inthe figures. The apparatus may be otherwise oriented (rotated 90 degreesor at other orientations) and the spatially relative descriptors usedherein may likewise be interpreted accordingly.

The present disclosure is generally related to methods for semiconductordevice fabrication, and more particularly to compositions ofphotosensitive layers in lithography and methods of using the same. Intypical lithography patterning, a resist layer (or film) is spin-coatedonto a substrate and is then exposed to a radiation. Subsequently, it isdeveloped in a developer (a chemical solution), which removes portions(such as exposed portions in a positive-tone photoresist or unexposedportions in a negative-tone photoresist) of the resist layer, therebyforming a resist pattern. The resist pattern is then used as an etchmask in subsequent etching processes, transferring the pattern to anunderlying material layer. Alternatively, the resist pattern may be usedas an ion implantation mask in subsequent ion implantation processesapplied to the underlying material layer, such as an epitaxialsemiconductor layer.

Generally, to act as an etch mask, the resist pattern must havesufficient etching resistance. A higher etching resistance is desirablewhen the resist pattern is used as an etch mask for etching a thickresist under-layer, such as a spin-on coated (SOC) layer having siliconor metal contents. However, existing photoresist materials generallyhave insufficient etching resistance for etching such thickunder-layers. To overcome this issue, typical lithography forms a thinhard mask layer between the resist pattern and the under-layer. Theresist pattern is used as an etch mask for etching the thin hard masklayer which is then used as an etch mask for etching the under-layer.The material and process associated with the additional hard mask layerincrease the total manufacturing costs. Thus, an object of the presentdisclosure is to provide new and improved photoresists that providehigher etching resistance than existing photoresists such that resistpatterns formed with the new and improved photoresists can be used fordirectly etching thick resist under-layers.

There are generally two types of processes for developing exposed resistlayers: a positive tone development (PTD) process and a negative tonedevelopment (NTD) process. In a PTD process, exposed areas of a resistlayer are dissolved and removed by a developer. In an NTD process,unexposed areas of a resist layer are dissolved and removed by adeveloper. The PTD and NTD processes may use different developers. Inthe present disclosure, “exposed” areas of a resist layer are thoseareas of the resist layer that are exposed to a radiation energy above apredetermined threshold value of the resist layer such that they becomeinsoluble (as in the NTD process) or soluble (as in the PTD process)after the exposure (and sometimes after a post-exposure baking (PEB)process as will be discussed later). Similarly, “unexposed” areas of aresist film are those areas of the resist film that remain soluble (asin the NTD process) or insoluble (as in the PTD process) after theexposure. An object of the present disclosure is to provide new andimproved photoresists for both PTD and NTD processes.

FIG. 1 is a flow chart of a method 100 of patterning a substrate (e.g.,a semiconductor wafer) according to various aspects of the presentdisclosure. The method 100 may be implemented, in whole or in part, by asystem employing deep ultraviolet (DUV) lithography, extreme ultraviolet(EUV) lithography, electron beam (e-beam) lithography, x-raylithography, ion beam lithography, and other lithography processes.Additional operations can be provided before, during, and after themethod 100, and some operations described can be replaced, eliminated,or moved around for additional embodiments of the method. The method 100is an example, and is not intended to limit the present disclosurebeyond what is explicitly recited in the claims.

In the following discussion, the method 100 is first described inconjunction with FIGS. 2A-2F wherein a semiconductor device 200 isfabricated by using embodiments of the method 100 in an NTD process.Then, the method 100 is described in conjunction with FIGS. 7A-7Fwherein a semiconductor device 400 is fabricated by using embodiments ofthe method 100 in a PTD process. Each of the semiconductor devices 200and 400 may be an intermediate device fabricated during processing of anIC, or a portion thereof, that may comprise SRAM and/or logic circuits,passive components such as resistors, capacitors, and inductors, andactive components such as diodes, field-effect transistors (FETs),p-type FETs (PFETs), n-type FETs (NFETs), fin-like FETs (FinFETs), otherthree-dimensional (3D) FETs, metal-oxide-semiconductor FETs (MOSFET),complementary MOSFETs (CMOS), bipolar transistors, high voltagetransistors, high frequency transistors, other memory cells, andcombinations thereof.

Referring now to FIG. 1, the method 100 (FIG. 1) is provided with asubstrate 202 (FIG. 2A) at operation 102. Referring to FIG. 2A, thesubstrate 202 includes one or more layers of material or composition. Inan embodiment, the substrate 202 is a semiconductor substrate (e.g.,wafer). In another embodiment, the substrate 202 includes silicon in acrystalline structure. In alternative embodiments, the substrate 202includes other elementary semiconductors such as germanium; a compoundsemiconductor such as silicon carbide, gallium arsenide, indiumarsenide, and indium phosphide; an alloy semiconductor such as GaAsP,AlInAs, AlGaAs, InGaAs, GaInP, and/or GaInAsP; or combinations thereof.The substrate 202 may include a silicon on insulator (SOI) substrate, bestrained/stressed for performance enhancement, include epitaxialregions, include isolation regions, include doped regions, include oneor more semiconductor devices or portions thereof, include conductiveand/or non-conductive layers, and/or include other suitable features andlayers.

In an alternative embodiment, the substrate 202 is a mask substrate thatmay include a low thermal expansion material such as quartz, silicon,silicon carbide, or silicon oxide-titanium oxide compound. To furtherthis example, the substrate 202 may be a mask substrate for making adeep ultraviolet (DUV) mask, an extreme ultraviolet (EUV) mask, or othertypes of masks.

At operation 104, the method 100 (FIG. 1) forms a material layer 204over the substrate 202 (FIG. 2B). Referring to FIG. 2B, in anembodiment, the material layer 204 includes a dielectric material suchas amorphous silicon (a-Si), silicon oxide, silicon nitride (SiN),titanium nitride, aluminum oxide, or other suitable material orcomposition. In an embodiment, the material layer 204 is ananti-reflection coating (ARC) layer such as a nitrogen-freeanti-reflection coating (NFARC) layer including material(s) such assilicon oxide, silicon oxygen carbide, or plasma enhanced chemical vapordeposited silicon oxide. In some embodiment, the substrate 202 includesa patterning layer as its top layer and the method 100 may skip theoperation 104 without forming the material layer 204.

At operation 106, the method 100 (FIG. 1) forms a photoresist (orresist) layer 206 over the substrate 202, and particularly over thematerial layer 204 in the present embodiment. Referring to FIG. 2C, inan embodiment, the resist layer 206 is formed by spin-on coating aliquid polymeric material over the material layer 204. In an embodiment,the resist layer 206 is further treated with a soft baking process and ahard baking process. In an embodiment, the resist layer 206 is sensitiveto a radiation, such as an I-line light, a DUV light (e.g., 248 nmradiation by krypton fluoride (KrF) excimer laser or 193 nm radiation byargon fluoride (ArF) excimer laser), a EUV light (e.g., 13.5 nm light),an e-beam, an x-ray, and an ion beam. Further in the present embodiment,the resist layer 206 is an NTD resist, i.e., its solubility in a NTDdeveloper decreases upon the radiation.

In an embodiment, the material layer 204 is also a polymeric materialand is also spin-on coated onto the substrate 202. To further thisembodiment, the material layer 204 and the resist layer 206 havedifferent optical properties with respect to the radiation. For example,the material layer 204 may have a substantially different refractiveindex (n), extinction coefficient (k), or spectroscopic transmittance(T) than the resist layer 206.

In the present embodiment, the resist layer 206 includes aphotosensitive chemical, a polymeric material having one or more acidlabile groups (ALG), and a solvent. The photosensitive chemical may be aphoto-acid generator (PAG) that produces an acid upon radiation. Theacid cleaves the ALGs off the polymeric material in a chemicalamplification reaction. In the present embodiment, the resist layer 206further includes a silicon-containing unit that can be chemically bondedto the polymeric material after the ALGs have been cleaved. Thesilicon-containing unit advantageously increases the etching resistanceof the resist layer 206 for subsequent etching processes.

FIG. 3A shows an embodiment of a resist material 300, in portion,included in the resist layer 206, constructed in accordance with someembodiments of the present disclosure. The resist material 300 includesa first polymer 302, a PAG 312, and a solvent 314. The first polymer 302includes a polymer backbone 304 and an ALG 306 chemically bonded to thepolymer backbone 304. In the present embodiment, the first polymer 302further includes a polar unit 308 and a first silicon-containing unit310, both of which are chemically bonded to the polymer backbone 304.The polar unit 308 is generally capable of increasing adhesion of theresist layer 206 with an under-layer such as the material layer 204. Insome embodiments, the polar unit 308 may be hydroxyl adamantane,norbornane lactone, γ-butyrolactone, and derivatives thereof. The firstsilicon-containing unit 310 serves to increase the etching resistance ofthe resist layer 206. In the present embodiment, the resist material 300further includes an etching resistance enhancement (ERE) unit 315. TheERE unit 315 includes a crosslinker 316 and a second silicon-containingunit 318 that is chemically bonded to the crosslinker 316. Thecrosslinker 316 and the silicon-containing unit 318 may be directlybonded or indirectly bonded through an intermediate bonding unit 320. Inthe present embodiment, the PAG 312 and the ERE 315 are blended with thepolymer 302 in the solvent 314. The blending of the various componentsin the solvent 314 may be done by a photoresist provider or at the siteof a semiconductor manufacturer. The ERE 315, particularly the secondsilicon-containing unit 318, serves to further increase the etchingresistance of the resist layer 206. This aspect will become more evidentafter the discussion of operation 108. In some embodiments, the resistmaterial 300 further includes a quencher for neutralizing excessiveacids produced by the PAG 312 and/or for suppressing resist outgassing.The quencher may be amine derivatives including primary, secondary,tertiary aliphatic or aromatic amine, in some embodiments. In somefurther embodiments, the resist material 300 includes a surfactant forreducing surface tension between the resist layer 206 and the materiallayer 204. In various embodiments, the molecular weight of the resistmaterial 300 ranges from 1,000 to 20,000.

At operation 108, the method 100 (FIG. 1) exposes the resist layer 206to a radiation beam 208 in a lithography system. Referring to FIG. 2D,some portions 206 a (shaded areas) of the resist layer 206 are exposedby the radiation beam 208, and other portions 206 b of the resist layer206 remain unexposed. The radiation beam 208 may be an I-line light (365nm), a DUV radiation such as KrF excimer laser (248 nm) or ArF excimerlaser (193 nm), a EUV radiation (e.g., 13.5 nm), an e-beam, an x-ray, anion beam, or other suitable radiations. Operation 108 may be performedin air, in a liquid (immersion lithography), or in a vacuum (e.g., forEUV lithography and e-beam lithography). In an embodiment, the radiationbeam 208 is patterned with a mask 210, such as a transmissive mask or areflective mask, which may include resolution enhancement techniquessuch as phase-shifting and/or optical proximity correction (OPC). Themask 210 includes various patterns for forming IC features in or on thesubstrate 202. In another embodiment, the radiation beam 208 is directlymodulated with a predefined pattern, such as an IC layout, without usinga mask (e.g., maskless lithography using e-beam).

In the present embodiment, the exposed portions 206 a undergo somechemical changes in response to the radiation 208. For example, withrespect to FIG. 3A, the PAG 312 releases an acid in response to theradiation 208. The acid cleaves the ALG 306 off the polymer backbone304, which makes the polymer 302 more hydrophilic. As a result, theexposed portions 206 a become insoluble in an organic developer, such asn-butyl acetate (n-BA). In some embodiments, the method 100 furtherperforms a post-exposure baking (PEB) process to the exposed resistlayer 206. The PEB process accelerates the above acid-generation andcleaving reactions. In an embodiment, the PEB process may be performedin a thermal chamber at a temperature ranging between about 120 degreesCelsius (° C.) to about 160° C.

In the present embodiment, the ERE unit 315 (FIG. 3A) is designed suchthat the crosslinker 316 reacts with the sites of the polymer backbone304 that have lost the ALG 306 due to the above cleaving reactions. Anet effect is that the ERE unit 315 replaces the ALG 306 during theexposure operation 108 and/or during the PEB process. A resultantpolymer 302A, in portion, is shown in FIG. 3B. Referring to FIG. 3B, inthe present embodiment, the polymer 302A includes the polymer backbone304 and the ERE unit 315 chemically bonded to the polymer backbone 304.The polymer 302A further includes the polar unit 308 and the firstsilicon-containing unit 310 that are chemically bonded to the polymerbackbone 304. The ALG 306 has been cleaved off the polymer backbone 304and will be removed in subsequent processes. The polymer 302Aadvantageously provides increased etching resistance to the exposedportions 206 a due to the inclusion of the second silicon-containingunit 318.

FIG. 4A shows an embodiment of another resist material 330, in portion,for the resist layer 206, constructed in accordance with someembodiments of the present disclosure. Referring to FIG. 4A, the resistmaterial 330 includes the polymer 302, the PAG 312, and the solvent 314as discussed with respect to FIG. 3A. The polymer 302 includes thepolymer backbone 304 with the ALG 306, the polar unit 308, and thesilicon-containing unit 310 chemically bonded with the polymer backbone304. The resist material 330 further includes an etching resistanceenhancement (ERE) unit 317. The ERE unit 317 includes two crosslinkers316 that are chemically bonded with one silicon-containing unit 318. Thetwo crosslinkers 316 may be directly bonded with the silicon-containingunit 318, or indirectly bonded with the silicon-containing unit 318through two intermediate bonding units 320.

FIG. 4B illustrates a portion of the structure of the resist material330 in the exposed portions 206 a. Referring to FIG. 4B, the ALGs 306have been cleaved off two polymers 302A and 302B, each of which is anexample of the polymer 302 of FIG. 4A. For example, the polymer 302Aincludes a polymer backbone 304A, a polar unit 308A, and a firstsilicon-containing unit 310A; while the polymer 302B includes a polymerbackbone 304B, a polar unit 308B, and a first silicon-containing unit310B. Further, the ERE unit 317 crosslinks the two polymers 302A and302B to form a larger polymer during the exposing operation 108 and/orthe subsequent PEB process. The ERE unit 317 provides not only extrasilicon contents but also larger polymers to the exposed portions 206 afor improving the etching resistance thereof.

In an embodiment, the crosslinker 316 of the resist materials 300 and330 comprises amine, aziridine, hydroxyl, aliphatic epoxy,cycloaliphatic epoxy, oxetane, or maleic anhydride. Exemplary chemicalstructures of the crosslinker 316 are shown in FIG. 5. In each of thechemical structures in FIG. 5, the symbol “L” represents theintermediate bonding unit 320.

In an embodiment, the silicon-containing unit 318 includessilicon-oxygen bonds. In an embodiment, the silicon-containing unit 318includes a silsesquioxane. For example, the silicon-containing unit 318may be a cage-type silsesquioxane such as shown in FIGS. 6A, 6B, 6C, and6D. The silicon-containing unit 318 may also be other types ofsilsesquioxane. For example, the silicon-containing unit 318 may be anincomplete-cage type silsesquioxane such as shown in FIG. 6E, a laddertype silsesquioxane such as shown in FIG. 6F, or a random typesilsesquioxane such as shown in FIG. 6G. In each of the FIGS. 6A-6G, thesymbol “R” represents the crosslinker 316 and the symbol “L” representsthe intermediate bonding unit 320.

In an embodiment, the intermediate bonding unit 320 has an aromatic ringstructure. Alternatively, the intermediate bonding unit 320 has a chainstructure with 0 to 6 carbon atoms. For example, the chain may be alinear chain or a cyclic chain. Further, the chain may comprise an alkylgroup, an alkoxy group, a fluoro alkyl group, or a fluoroalkoxy group.

At operation 110, the method 100 (FIG. 1) develops the exposed resistlayer 206 in a developer 212 (FIG. 2E). Referring to FIG. 2E, unexposedportions 206 b are removed by the developer 212 (negative tone imaging),leaving the exposed portions 206 a over the material layer 204 as aresist pattern 206 a. In some embodiments, the resist layer 206experiences a polarity change after the operation 108 and/or the PEBprocess discussed above, and a dual-tone developing process may beimplemented. In some examples, the resist layer 206 is changed from anonpolar state (hydrophobic state) to a polar state (hydrophilic state),then the unexposed portions 206 b will be removed by an organic solvent,such as n-BA or its derivative. In some other examples, the resist layer206 is changed from a polar state to a nonpolar state, then theunexposed portions 206 b will be removed by an aqueous solvent such ashaving 2.38% tetramethyl ammonium hydroxide (TMAH).

At operation 112, the method 100 (FIG. 1) transfers the resist pattern206 a to the substrate 202. Referring to FIG. 2F, in the presentembodiment, the operation 112 includes etching the material layer 204with the resist pattern 206 a as an etch mask, thereby transferring thepattern from the resist pattern 206 a to the material layer 204. In anembodiment, the material layer 204 is a spin-on coated layer havingmetal or silicon contents. Due to the increased etching resistance ofthe resist pattern 206 a, the operation 112 is able to fully etch thematerial layer 204 to from a pattern 204 a. The operation 112 may use adry (plasma) etching, a wet etching, or other suitable etching methods.For example, a dry etching process may implement an oxygen-containinggas, a fluorine-containing gas (e.g., CF₄, SF₆, CH₂F₂, CHF₃, and/orC₂F₆), a chlorine-containing gas (e.g., Cl₂, CHCl₃, CCl₄, and/or BCl₃),a bromine-containing gas (e.g., HBr and/or CHBR₃), an iodine-containinggas, other suitable gases and/or plasmas, and/or combinations thereof.The resist pattern 206 a may be partially consumed during the etching ofthe material layer 204. In an embodiment, any remaining portion of theresist pattern 206 a may be stripped off, leaving the patterned materiallayer 204 a over the substrate 202, as illustrated in FIG. 2F.

FIGS. 7A-7F illustrate cross-sectional views of the semiconductor device400 during various stages of fabrication according to an embodiment ofthe method 100 in a PTD process. Referring to FIGS. 1 and 7A, the method100 is provided with a substrate 402 at operation 102. The substrate 402may be similar to the substrate 202. Referring to FIGS. 1 and 7B, themethod 100 forms a material layer 404 over the substrate 402 atoperation 104. The material layer 404 may be similar to the materiallayer 204. However, various properties of the material layer 404 aredesigned to work with a resist layer 406 to be formed thereon.

Referring to FIGS. 1 and 7C, the method 100 forms a photoresist (orresist) layer 406 over the substrate 402, and particularly over thematerial layer 404 in the present embodiment. In an embodiment, theresist layer 406 is formed by spin-on coating a liquid polymericmaterial over the material layer 404. In an embodiment, the resist layer406 is further treated with a soft baking process and a hard bakingprocess. In an embodiment, the resist layer 406 is sensitive to aradiation, such as an I-line light, a DUV light (e.g., 248 nm radiationby krypton fluoride (KrF) excimer laser or 193 nm radiation by argonfluoride (ArF) excimer laser), a EUV light (e.g., 13.5 nm light), ane-beam, an x-ray, and an ion beam. Further in the present embodiment,the resist layer 406 is a PTD resist, i.e., its solubility in a PTDdeveloper increases upon the radiation.

In an embodiment, the material layer 404 is also a polymeric materialand is spin-on coated onto the substrate 402. To further thisembodiment, the material layer 404 and the resist layer 406 havedifferent optical properties with respect to the radiation. For example,the material layer 404 may have a substantially different refractiveindex (n), extinction coefficient (k), or spectroscopic transmittance(T) from the resist layer 406.

In the present embodiment, the resist layer 406 includes aphotosensitive chemical, a polymeric material having one or more acidlabile groups (ALG), and a solvent. The photosensitive chemical may be aphoto-acid generator (PAG) that produces an acid upon radiation. Theacid cleaves the ALGs off the polymeric material in a chemicalamplification reaction. In the present embodiment, the resist layer 406further includes a silicon-containing unit that is chemically bonded tothe ALG. The silicon-containing unit advantageously increases theetching resistance of unexposed portions of the resist layer 406 forsubsequent etching processes.

FIG. 8A shows an embodiment of a resist material 500, in portion, thatis included in the resist layer 406, constructed in accordance with someembodiments of the present disclosure. Referring to FIG. 8A, the resistmaterial 500 includes a first polymer 502, a PAG 512, and a solvent 514.The first polymer 502 includes a polymer backbone 504 and an ALG 506chemically bonded to the polymer backbone 504. In the presentembodiment, the first polymer 502 further includes a polar unit 508chemically bonded to the polymer backbone 504. The polar unit 508 isgenerally capable of increasing adhesion of the resist layer 406 with anunder-layer such as the material layer 404. In some embodiments, thepolar unit 508 may be hydroxyl adamantane, norbornane lactone,γ-butyrolactone, and derivatives thereof. In the present embodiment, theresist material 500 further includes a silicon-containing unit 518 thatis chemically bonded to the ALG 506. The silicon-containing unit 518 maybe directly bonded to the ALG 506 or indirectly bonded to the ALG 506through an intermediate bonding unit 520. The silicon-containing unit518 serves to increase the etching resistance of the resist layer 406.In the present embodiment, the PAG 512 is blended with the polymer 502in the solvent 514. The blending of the various components in thesolvent 514 may be done by a photoresist provider or at the site of asemiconductor manufacturer. In some embodiments, the resist material 500further includes a quencher for neutralizing excessive acids produced bythe PAG 512 and/or for suppressing resist outgassing. The quencher maybe amine derivatives including primary, secondary, tertiary aliphatic oraromatic amine, in some embodiments. In some further embodiments, theresist material 500 includes a surfactant for reducing surface tensionbetween the resist layer 406 and the material layer 404. In variousembodiments, the molecular weight of the resist material 500 ranges from1,000 to 20,000.

Referring to FIGS. 1 and 7D, the method 100 exposes the resist layer 406to a radiation beam 408 in a lithography system. Some portions 406 a(shaded areas) of the resist layer 406 are exposed by the radiation beam408, and other portions 406 b of the resist layer 406 remain unexposed.The radiation beam 408 may be an I-line light (365 nm), a DUV radiationsuch as KrF excimer laser (248 nm) or ArF excimer laser (193 nm), a EUVradiation (e.g., 13.5 nm), an e-beam, an x-ray, an ion beam, or othersuitable radiations. Operation 108 may be performed in air, in a liquid(immersion lithography), or in a vacuum (e.g., for EUV lithography ande-beam lithography). In an embodiment, the radiation beam 408 ispatterned with a mask 410, such as a transmissive mask or a reflectivemask, which may include resolution enhancement techniques such asphase-shifting and/or optical proximity correction (OPC). The mask 410includes various patterns for forming IC features in or on the substrate402. In another embodiment, the radiation beam 408 is directly modulatedwith a predefined pattern, such as an IC layout, without using a mask(e.g., maskless lithography using e-beam).

In the present embodiment, the exposed portions 406 a undergo somechemical changes in response to the radiation 408. For example, withrespect to FIG. 8A, the PAG 512 releases an acid in response to theradiation 408. The acid cleaves the ALG 506 off the polymer backbone 504as illustrated in FIG. 8B, which makes the polymer 402 more hydrophilic.As a result, the exposed portions 406 a become soluble in an aqueoussolution, such as having 2.38% TMAH. In some embodiments, the method 100further performs a post-exposure baking (PEB) process to the exposedresist layer 406. The PEB process accelerates the above acid-generationand cleaving reactions. In an embodiment, the PEB process may beperformed in a thermal chamber at a temperature ranging between about120° C. to about 160° C.

In an embodiment, the silicon-containing unit 518 includessilicon-oxygen bonds. In an embodiment, the silicon-containing unit 518includes a silsesquioxane. For example, the silicon-containing unit 518may be a cage-type silsesquioxane such as shown in FIGS. 6A, 6B, 6C, and6D. The silicon-containing unit 518 may also be other types ofsilsesquioxane. For example, the silicon-containing unit 518 may be anincomplete-cage type silsesquioxane such as shown in FIG. 6E, a laddertype silsesquioxane such as shown in FIG. 6F, or a random typesilsesquioxane such as shown in FIG. 6G. In each of the FIGS. 6A-6G, thesymbol “L” represents the intermediate bonding unit 520 and the symbol“R” represents the ALG 506.

In an embodiment, the intermediate bonding unit 520 has an aromatic ringstructure. Alternatively, the intermediate bonding unit 520 has a chainstructure with 0 to 6 carbon atoms. For example, the chain may be alinear chain or a cyclic chain. Further, the chain may comprise an alkylgroup, an alkoxy group, a fluoro alkyl group, or a fluoroalkoxy group.

In an embodiment, the ALG 506 is a cyclopentane, a cyclohexane, anadamantane, a norbornane, or a derivative thereof. Typically, thecontents of the ALG 506 in the resist material 500 are high. By bondingthe silicon-containing unit 518 to the ALG 506, embodiments of thepresent disclosure substantially increase the etching resistance of theunexposed portions 406 b.

Referring to FIGS. 1 and 7E, the method 100 develops the exposed resistlayer 406 in a developer 412. The exposed portions 406 a are removed bythe developer 412 (positive tone imaging), leaving the unexposedportions 406 b over the material layer 404 as a resist pattern 406 b. Insome embodiments, the resist layer 406 experiences a polarity changeafter the operation 108 and/or the PEB process discussed above, and adual-tone developing process may be implemented. In some examples, theresist layer 406 is changed from a nonpolar state (hydrophobic state) toa polar state (hydrophilic state), then the exposed portions 406 a willbe will be removed by an aqueous solvent such as having 2.38% TMAH. Insome other examples, the resist layer 406 is changed from a polar stateto a nonpolar state, then the exposed portions 406 a will be removed byan organic solvent, such as n-BA or its derivative.

Referring to FIGS. 1 and 7F, the method 100 transfers the resist pattern406 b to the substrate 402. In the present embodiment, the operation 112includes etching the material layer 404 with the resist pattern 406 b asan etch mask, thereby transferring the pattern from the resist pattern406 b to the material layer 404. In an embodiment, the material layer404 is a spin-on coated layer having metal or silicon contents. Due tothe increased etching resistance of the resist pattern 406 b, theoperation 112 is able to fully etch the material layer 404 to from apattern 404 b. The operation 112 may use a dry (plasma) etching, a wetetching, or other suitable etching methods. The resist pattern 406 b maybe partially consumed during the etching of the material layer 404. Inan embodiment, any remaining portion of the resist pattern 406 b may bestripped off, leaving a patterned material layer 404 b over thesubstrate 402, as illustrated in FIG. 7F.

Although not shown in FIG. 1, the method 100 may proceed to etching thesubstrate 202 or 402 with the patterned material layer 204 a or 404 b,respectively, as an etch mask, thereby forming a final pattern or an ICdevice on the substrate 202 or 402. For example, the method 100 may formshallow trench isolation (STI) features for defining transistor activeregions, may form fin-like protrusions in the respective substrates forforming FinFETs, may form contact holes for transistor source/drain/gatecontacts, and may form interconnect features.

Although not intended to be limiting, one or more embodiments of thepresent disclosure provide many benefits to semiconductorphotolithography processes. For example, a resist material orcomposition constructed according to the present disclosure may be usedfor forming a resist pattern with increased etching resistance. Thisresist pattern may be used for directly etching a thick spin-on coatedunder-layer in photolithography, thereby saving manufacturing costs.

In one exemplary aspect, the present disclosure is directed to a methodfor lithography patterning. The method includes forming a photoresistlayer over a substrate, wherein the photoresist layer includes a polymerbackbone, an acid labile group (ALG) chemically bonded to the polymerbackbone, a photo-acid generator (PAG), a solvent, and asilicon-containing unit chemically bonded to a crosslinker. The methodfurther includes performing an exposing process to the photoresistlayer; and developing the photoresist layer, thereby forming a patternedphotoresist layer.

In another exemplary aspect, the present disclosure is directed to amethod for lithography patterning. The method includes forming aphotoresist layer over a substrate, wherein the photoresist layerincludes a polymer backbone, an acid labile group (ALG) chemicallybonded to the polymer backbone, a photo-acid generator (PAG), a solvent,and a silicon-containing unit chemically bonded to the ALG. The methodfurther includes performing an exposing process to the photoresistlayer; and developing the photoresist layer, thereby forming a patternedphotoresist layer.

In another exemplary aspect, the present disclosure is directed to aphotoresist. The photoresist comprises a polymer backbone, an acidlabile group (ALG) chemically bonded to the polymer backbone, aphoto-acid generator (PAG), a solvent, and a silicon-containing unitthat is chemically bonded to one of: the ALG and a crosslinker.

The foregoing outlines features of several embodiments so that those ofordinary skill in the art may better understand the aspects of thepresent disclosure. Those of ordinary skill in the art should appreciatethat they may readily use the present disclosure as a basis fordesigning or modifying other processes and structures for carrying outthe same purposes and/or achieving the same advantages of theembodiments introduced herein. Those of ordinary skill in the art shouldalso realize that such equivalent constructions do not depart from thespirit and scope of the present disclosure, and that they may makevarious changes, substitutions, and alterations herein without departingfrom the spirit and scope of the present disclosure.

What is claimed is:
 1. A method for lithography patterning, comprising:forming a photoresist layer over a substrate, wherein the photoresistlayer includes a polymer backbone, an acid labile group (ALG) chemicallybonded to the polymer backbone, a photo-acid generator (PAG), a solvent,and a silicon-containing unit chemically bonded to a crosslinker;performing an exposing process to the photoresist layer; and developingthe photoresist layer to remove portions of the photoresist layer thatare not exposed by the exposing process, thereby forming a patternedphotoresist layer.
 2. The method of claim 1, further comprising: bakingthe photoresist layer before the developing of the photoresist layer. 3.The method of claim 1, wherein the silicon-containing unit is chemicallybonded to the crosslinker through an intermediate bonding unit.
 4. Themethod of claim 3, wherein the intermediate bonding unit is an aromaticring or a chain with 1 to 6 carbon atoms.
 5. The method of claim 4,wherein the chain comprises an alkyl group, an alkoxy group, a fluoroalkyl group, or a fluoroalkoxy group.
 6. The method of claim 1, whereinthe crosslinker comprises amine, aziridine, hydroxyl, aliphatic epoxy,cycloaliphatic epoxy, oxetane, or maleic anhydride.
 7. The method ofclaim 1, wherein the silicon-containing unit comprises a silsesquioxane.8. The method of claim 7, wherein the silsesquioxane is a cagesilsesquioxane, an incomplete cage silsesquioxane, a laddersilsesquioxane, or a random silsesquioxane.
 9. The method of claim 1,wherein the silicon-containing unit is also chemically bonded to anothercrosslinker.
 10. The method of claim 1, wherein the photoresist layerfurther includes another silicon-containing unit that is chemicallybonded to the polymer backbone.
 11. The method of claim 1, wherein thephotoresist layer further includes a polar unit that is chemicallybonded to the polymer backbone, the polar unit comprising hydroxyladamantine, norbornane lactone, γ-butyrolactone, or derivatives thereof.12. A method for lithography patterning, comprising: forming aphotoresist layer over a substrate, wherein the photoresist layerincludes a polymer backbone, a first silicon-containing unit chemicallybonded to the polymer backbone, an acid labile group (ALG) chemicallybonded to the polymer backbone, a photo-acid generator (PAG), a solvent,and a second silicon-containing unit chemically bonded to a crosslinker,wherein the crosslinker is bondable to the polymer backbone if the ALGis cleaved off thereof; performing an exposing process to thephotoresist layer, resulting in the ALG being cleaved off of the polymerbackbone and the crosslinker bonding to the polymer backbone; anddeveloping the photoresist layer to remove portions of the photoresistlayer that are not exposed by the exposing process, thereby forming apatterned photoresist layer.
 13. The method of claim 12, wherein thecrosslinker comprises amine, aziridine, hydroxyl, aliphatic epoxy,cycloaliphatic epoxy, oxetane, or maleic anhydride.
 14. The method ofclaim 12, wherein the second silicon-containing unit comprises a cagesilsesquioxane, an incomplete cage silsesquioxane, a laddersilsesquioxane, or a random silsesquioxane.
 15. The method of claim 12,wherein the second silicon-containing unit is also chemically bonded toanother crosslinker that is bondable to the polymer backbone after theALG is cleaved off therefrom.
 16. The method of claim 12, wherein thephotoresist layer further includes a polar unit that is chemicallybonded to the polymer backbone, the polar unit comprising hydroxyladamantine, norbornane lactone, γ-butyrolactone, or derivatives thereof.17. The method of claim 12, wherein the second silicon-containing unitis chemically bonded to the crosslinker through an intermediate bondingunit, the intermediate bonding unit is a chain comprising a fluoro alkylgroup, or a fluoroalkoxy group.
 18. A method for lithography patterning,comprising: forming a photoresist layer over a substrate, wherein thephotoresist layer includes a polymer backbone, a firstsilicon-containing unit chemically bonded to the polymer backbone, apolar unit chemically bonded to the polymer backbone, an acid labilegroup (ALG) chemically bonded to the polymer backbone, a photo-acidgenerator (PAG), a solvent, and a second silicon-containing unitchemically bonded to a crosslinker; performing an exposing process tothe photoresist layer; and developing the photoresist layer, therebyforming a patterned photoresist layer, wherein the polar unit compriseshydroxyl adamantine, norbornane lactone, γ-butyrolactone, or derivativesthereof.
 19. The method of claim 18, wherein the ALG is cyclopentane,cyclohexane, adamantane, norbornane, or a derivative thereof.
 20. Themethod of claim 18, wherein the photoresist layer becomes morehydrophilic if the ALG is cleaved off of the polymer backbone.